Hey everybody. Our 2002 Yukon XL that we use here in AZ for towing boats has started doing something very strange. We had the whole top end rebuilt, radiator, water pump, thermostat, coolant tank, and fan clutch replaced. So the whole cooling system. Being 105F+ here, the truck actually runs great. It has 258K miles on it and my mechanic is amazed on how well it runs. We originally had all of the above done because it was overheating at idle.
Now, after all the work, it still overheats. But with one strange thing…. only when the rear AC is on. If that is off, and the temp. knob is turned to about half way, the truck runs nice and cool. Any time the rear AC is turned on to cold and the fan is put on, the engine overheats.
As far as the front AC goes, it does NOT overheat when it is on. The AC also doesn't blow very cold from the FRONT when the AC in the REAR IS OFF. Once the rear is on, the front gets ice cold, but then the car overheats.
Very strange situation here and even my mechanic is confused. Anyone else know what it could be? We aren't ruling out a crack in the block either, even though that seems very unlikely.
Now, after all the work, it still overheats. But with one strange thing…. only when the rear AC is on. If that is off, and the temp. knob is turned to about half way, the truck runs nice and cool. Any time the rear AC is turned on to cold and the fan is put on, the engine overheats.
As far as the front AC goes, it does NOT overheat when it is on. The AC also doesn't blow very cold from the FRONT when the AC in the REAR IS OFF. Once the rear is on, the front gets ice cold, but then the car overheats.
Very strange situation here and even my mechanic is confused. Anyone else know what it could be? We aren't ruling out a crack in the block either, even though that seems very unlikely.
